Background: The recommended capillary TSH cut-off level for neonatal screening for congenital hypothyroidism (CH) in the UK is 10 mIU/l. However several of the regional screening laboratories have adopted lower cut-off limits in order to increase detection sensitivity. There is now pressure to standardise the UK screening programme with universal adoption of the recommended cut-off. Scotland has been using a cut-off of 8 mIU/l since the adoption of AutoDELFIA TSH screening methodology in Autumn 2003. We wished to examine what difference this lower cut-off point has made to detection of congenital hypothyroidism.
Methods and design: The national congenital hypothyroidism database was searched for cases in which the first or subsequent capillary TSH (cTSH) results fell between 8.0 and 10.0 mIU/l between January 2004 and 2014. The outcome of these cases was then examined.
Results: There were 304 referrals for cTSH of any value in the study period. Twenty-five (8.2%) referrals were made because of a cTSH between 8.0 and 10.0 mIU/l. Of these, 13 (52%) have since proven to have had transient elevated TSH in the neonatal period. A further 6 (24%) cases have permanent forms of CH (two thyroid ectopia with compensated hypothyroidism, two dyshormonogenesis and decompensated hypothyroidism, two unknown cause: one decompensated pre-treatment; the other on 100 μg/day thyroxine at seven years of age). The remainder 6 (24%) have no final diagnosis, either because they are still awaiting diagnostic challenge (n=2), because the challenge was inconclusive (n=2) or data was not available.
Conclusion: Less than 10% of referrals made were due to a cTSH of between 8.0 and <10.0 mIU/l. Unsurprisingly, a significant proportion of these referrals proved to be transient neonatal hyperthyrotropinaemia. However one quarter of all referrals made based on a cTSH of between 8.0 and <10.0 mIU/l had permanent forms of CH including both dysgenesis and dyshormonogenesis. Half of the referrals made in this group had decompensated CH at pre-treatment assessment. Thus we would find it difficult to adopt the recommended UK cut-off of 10 mIU/l.
20 - 22 Sep 2014
European Society for Paediatric Endocrinology